The present invention relates to conveyor belt pulleys, and more particularly, to self-cleaning wing pulleys that are suited for bulk material handling applications.
In many types of conveyor applications, material can stick to or become entrapped behind the conveyor belt. When material is behind the conveyor belt, it is considered debris that must be displaced from the system for optimum conveyor belt traction and belt life.
The use of traditional straight, steep angled spiral, or symmetrically opposite angled wing pulleys is common in a wide variety of bulk materials handling applications. All three of these pulleys are constructed from materials and thicknesses that are appropriate for the size and rigor of the final application.
The traditional straight wing pulley is the original wing pulley. It is designed with plurality of radially spaced straight wings and wing tips that run the entire length of the pulley parallel to the central axis of rotation and perpendicular to the direction of belt travel. The design and manufacture of the traditional straight wing pulley is guided by ANSI/CEMA (American National Standards Institute/Conveyor Equipment Manufacturing Association) 501.1-2003(R2009) Specifications for Welded Steel Wing Pulleys.
The traditional straight wing pulley breaks material loose from the backside of the belt through the impact of the wing tips on the belt, but the debris falls between the wings of the pulley, where it can becomes trapped and recirculates between the belt and pulley. Additionally, traditional straight wing pulleys can have wing fold-over failures when heavy loads are applied due to the straight wings being perpendicular the direction of belt travel.
Steep angled spiral wing pulleys were introduced shortly after the traditional straight wing pulley in order to provide a wing pulley that would allow debris to enter the pulley and then slowly work its way out of the pulley. The original method for creating a spiral wrap was to attach a strap of flat material to the outside of a traditional straight wing pulley from a single start point at the center of the pulley. The strap was started at the center of the pulley and wrapped outward helically at a steep angle, generally 75 degrees or greater when measured in relation to the central axis of the pulley. This spiral wrap is duplicated on the second half of the pulley to create a symmetrically opposite wrap starting from a single start point. While the steep angle spiral assists by allowing debris to enter the pulley and slowly work outward, this does not align with more recent pulley designs that focus on rapid debris removal from a conveyor system.
The symmetrically opposite angled wing pulleys are the second generation of wing pulleys that have been found to clear debris up to 40× faster than traditional straight wing pulley. They are designed with wings that are formed or positioned at angles that are generally symmetrically opposite from the center of the pulley in an outward direction. This design moves material that falls between the wing and belt outward equally towards both ends of the pulley to eliminate recirculation of debris. The strength of the pulley is increased by the way the wings support the belt at an angle to the axis of rotation and belt travel. The limitations of the pulley are that the wings of the pulley must be symmetrically opposite for the conveyor belt to track properly and the pulley can only be operated in one direction of rotation. If the pulley is installed backwards or operated in a reversing application the symmetrically opposite angled wings will pull the debris inward to the center of the pulley at an accelerated rate, defeating the purpose of a wing pulley and potentially causing damage to the pulley and the conveyor belt.